1. Field of the Invention
The present invention relates to a liquid crystal composition and to a liquid crystal element having a liquid crystal layer containing the liquid crystal composition, and, particularly, to a liquid crystal element which can be preferably used for a guest-host system liquid crystal element.
2. Description of the Related Art
With regard to liquid crystal elements (liquid crystal display elements), many systems have been already proposed. Guest-host system liquid crystal elements enable bright display and are therefore expected to provide liquid crystal elements suitable to a reflection type. In the guest-host system liquid crystal elements, a dichroic dye is dissolved in a liquid crystal, and a light absorption state of the element is made to change based on a change in the orientation of the dichroic dye in accordance with the movement of the liquid crystal in response to an electric field, in order to display an image.
There are descriptions regarding the guest-host system in, for example, B. Bahadur, Handbook of Liquid Crystals, edited by D. Demus, J. Goodby, G. W. Gray, H. W. Spiess and V. Vill, vol. 2A, Willey-VCH, (1998), chapters 3 and 4, pages 257 to 302. It is required that the dichroic dye used for a guest-host system liquid crystal element have proper absorbing characteristics, high-order parameters, high solubility in a host liquid crystal, durability and the like.
As the dichroic dye, for example, an anthraquinone dye has been widely studied, and this dye is disclosed in, for instance, A. V. Ivashchenko, Dichroic Dyes for Liquid Crystal Display, CRC, 1994. However, many anthraquinone dyes have a low absorption coefficient and low solubility in a host liquid crystal, and earnest studies have been made by many researchers to improve the drawbacks of the anthraquinone dyes. Results of these studies are described in, for example, Jpn. J. Appl. Phys. vol. 37., page 3422 (1998).
In the meantime, phenoxazine dyes have a high absorption coefficient and a sharp hue and have therefore been widely studied as fluorescent dyes. Phenoxazine dyes as laser dyes are disclosed in the specification of U.S. Pat. No. 3,731,222. However, it is nowhere suggested that the phenoxazine dyes are used for liquid crystal compositions and liquid crystal elements.